1. Technical Field
The present disclosure relates to a thermoacoustic device, especially a thermoacoustic device based on carbon nanotubes.
2. Description of Related Art
In traditional speakers, sounds are produced by mechanical movement of one or more diaphragms.
In one article, entitled “The thermophone as a precision source of sound” by H. D. Arnold and I. B. Crandall, Phys. Rev. 10, pp 22-38 (1917), a thermophone based on the thermoacoustic effect is disclosed. The thermophone in the article includes a platinum strip used as sound wave generator and two terminal clamps. The two terminal clamps are located apart from each other, and are electrically connected to the platinum strip. The platinum strip has a thickness of 0.7 micrometers. Frequency response range and sound pressure of sound wave are closely related to the heat capacity per unit area of the platinum strip. The higher the heat capacity per unit area, the narrower the frequency response range and the weaker the sound pressure. An extremely thin metal strip such as a platinum strip is difficult to produce. For example, the platinum strip has a heat capacity per unit area higher than 2×10−4 J/cm2*K. The highest frequency response of the platinum strip is only 4×103 Hz, and the sound pressure produced by the platinum strip is also too weak and is difficult to be heard by human.
In another article, entitled “Flexible, Stretchable, Transparent Carbon Nanotube Thin Film Loudspeakers” by Fan et al., Nano Letters, Vol. 8 (12), 4539-4545 (2008), a carbon nanotube speaker is disclosed. The carbon nanotube speaker includes a sound wave generator. The sound wave generator is a carbon nanotube film. The carbon nanotube speaker can produce a sound that can be heard because of a large specific surface area and small heat capacity per unit area of the carbon nanotube film. The frequency response range of the carbon nanotube speaker can range from about 100 Hz to about 100 KHz. However, carbon nanotube speakers are not convenient for use.
What is needed, therefore, is to provide a carbon nanotube speaker which is convenient for use.